This invention relates generally to a load carrying apparatus which is inflatable from a collapsed configuration to an inflated airfoil configuration by RAM air upon deployment. Such devices have generally been viewed as gliding wing or parachute devices.
The various terminology used throughout this specification will follow the definitions, insofar as they are applicable, as adopted by the Parachute Industry Association in its PIA Technical Standard, adopted Jan. 23, 1984, a copy of which is attached hereto as Appendix A.
RAM air inflatable gliding wings are familiar forms of high glide parachutes in the prior art. These parachutes are characterized by wing type planforms and airfoil type cross sections. Typical canopy embodiment consists of patterned membrane components which in profile emulate the components of conventional airfoil wing design. Emphasis has been to approach a conventional airfoil profile during operation in an effort to optimize glide ratio and ability to carry a heavy load.
High glide parachutes have been developed for: Fire & Rescue Operations, Aerial Supply, Sport Skydiving, Emergency Escape Contingencies and numerous Aerospace and Military applications. These examples require rapid deceleration capability of the parachute system in addition to high glide and load carrying capability. Objectives found in the prior art which enhance glide and ability to carry heavy loads of typical high glide parachutes often limit structural performance of the design and in many instances have increased opening force characteristics which reduce utility or place additional reliance upon external reefing systems to enable parachute deployment capability.
Typical prior art canopy fabrication consists of components which include fabricated upper and lower surface panels which are held in place by internal airfoil dimensioned ribs, series spaced, creating chord wise positioned box-type containment cells. Assembly of components is usually accomplished using interlocking T-beam, I-beam, or half-cell chord-wise techniques along with various sewn seams. Single surface stabilizer panels have been used to terminate canopy wingtip ends attaching below outer airfoil ribs along chord-wise seams. During operation of the parachute, the containment cells become inflated by RAM air conducted by openings along the leading edge. Containment cells are able to pressure equalize by means of crossport cutouts made through the airfoil ribs. Vertical or diverging stress tapes are commonly utilized on airfoil ribs selected for flight load attachments. Such tapes extend upwardly from desired suspension attachment points and terminate just beneath the upper surface panel fabric. Suspension loops are sewn onto airfoil rib seams with suspension line connection accomplished by tying the lines onto the loops and securing the ends of line with stitching. Rigging configuration usually has line connections made to every other rib position across the canopy by span. This results in cells as having an unsupported or non-loaded airfoil rib positioned between cell defining load attachments. Substantially non-stretch suspension lines connect the high glide canopy to a harnessed object or point of load and transfer force. The lines are of precise dimensioned lengths so as to establish optimal trim angle for the canopy along with optimal span wise/chord wise camber profile angles. Generally, the suspension lines are cascaded to reduce drag as well as weight and bulk. Steering and in-flight modulation of aileron effect are accomplished by activation of separate control lines (left and right) which branch off from object location to selected positions along their respective trailing edge connection points.
Typical examples of such structures are shown in the PIA Technical Standard 100, Appendix A and also in U.S. Pat. Nos. 3,524,613, 3,558,087, 3,749,337, 3,893,641, 4,470,567, 4,705,238, 4,730,796, 4,771,970, 4,811,920, 4,865,272, 4,930,726. In addition to the foregoing U.S. Pat. Nos., the following foreign patents also disclose similar structures: French Patent 2 614 267, issued Oct. 28, 1988; European Patent 0 336 277, issued Mar. 29, 1989; French Patent 2 633 248, issued Dec. 29, 1989 and French Patent 2 614 268, issued Oct. 28, 1988.
RAM air inflatable wings or parachutes commonly utilize openings along the leading edge to provide direct inflation access to the containment airfoil section of the canopy. Inflation, deflation, and reinflation of the containment section may be accomplished in rapid sequence using this construction. In some instances, high glide parachutes have utilized openings along the leading edge and/or on the lower surface along with non-return valves to prevent containment section deflation during various inflight conditions or events. Examples of such structures are shown particularly in U.S. Pat. No. 3,558,087 and the European and French Patents above-identified.
Non-return valves serve to dampen containment response to reduced pressure events by blocking openings thus preventing escape of containment pressure from within the containment section. Due to pressure leakage through the sewn seams and fabric permeability, this effect is transient but can permit flight continuation beyond sudden events which can interrupt the flight of canopies which are not equipped with such non-return valve designs. Structures utilizing non-return valve configurations found in the prior art can be exposed to additional force and stress loads from events of substantial pressure environments such as a parachute deployment. Substantial pressure events can result in over-pressurization of the containment section. Size and/or placement reductions made to non-return valve structures in an effort to combat over-pressurization can adversely affect inflation or reinflation needs.
While the structures disclosed in the foregoing prior art references function adequately in many operational circumstances, it has been found that a great need still exists for a RAM air inflatable wing or high glide parachute that exhibits even better safety, strength, stability and maneuverability than the devices disclosed in the prior art. It has been found that the prior art devices do not adequately maintain their proper airfoil shape under all operational conditions. This inadequacy is caused primarily from induced airfoil distortions resulting from applied loads impacting the canopy at the point of line attachment. This condition, as well as the typical open leading edge, produces less efficient airfoil performance due to induced drag. As above described, prior art devices utilize conventional ribs and surface skins to form a plurality of interconnected box-shaped hollow tubes each of which, when filled with air, try to become rounded and distorted. This coupled with the load attachment point distortion results in varying and reduced airfoil efficiency. Utilizing prior art devices of the type above-disclosed, precise maneuvers of the type contemplated during sport parachuting are hindered by the less than optimal airfoil configuration of the canopies.
In addition to the foregoing, the maximum velocity at which the presently known RAM air inflated wings or parachutes can be deployed is limited by the load-bearing capability and excessive force generating characteristics thereof. Prior art devices must be reefed or prevented from excessively rapid inflation in order to lower forces experienced by the load. Possible destructive or catastrophic damage to the device limits its deployment airspeed capability or the velocity decay ratio usage.